Prevalence and molecular characterization of Listeria spp. and Listeria monocytogenes isolated from fish, shrimp, and cooked ready-to-eat (RTE) aquatic products in Iran

The prevalence of Listeria spp. and Listeria monocytogenes was investigated by biochemical and molecular methods in a total of 201 fish, shrimp, and ready-to-eat seafood samples collected from Iranian supermarkets. Thirty-six samples were also collected from a seafood processing plant. Twenty-one (8.86) of the total retail and processing plant samples (237) were positive for Listeria spp., confirmed by a simplex PCR assay for the prs gene. Seven (2.95) of the total samples were also positive for L. monocytogenes. The presence of four virulence-associated genes in the seafood isolates (inlA, inlC, inlJ, and hlyA) was examined using PCR and the results were compared with seven clinical L. monocytogenes strains. All virulence genes were detected in six fish isolates. One fish isolate did not show amplification of the inlJ and inlC genes. However, all seven clinical strains were positive for internalin genes. Furthermore, a multiplex PCR assay was employed to evaluate the major L. monocytogenes genoserogroups' distribution. The results revealed that the serotypes of lineage II are most frequently present in clinical and food isolates. In summary, PCR screening for both the major L. monocytogenes serovars and virulence genes revealed the potential public health risk posed by L. monocytogenes in aquatic products. © 2016 Elsevier Ltd

Modelling of Particulate Matter Transformations and Capture Efficiency

In the current work, a comprehensive computational fluid dynamics (CFD) model is developed for an accurate description of the transport and transformation of automotive particulate matter (PM) in monolithic reactors. The model accounts for the developing gas flow, the evaporation of hydrocarbons (HCs) from the particles, and the adsorption of HCs in the washcoat, as well as motion, shrinkage, and deposition of particles in the channel. The comprehensive CFD model is used to validate a simplified tanks-in-series approach with a conceptual model for PM transformations. In the development of more detailed and accurate chemical kinetics for the reactions of PM in filters, it will be necessary to also predict the time-resolved properties of the particles collected in the filter (e. g., reactivity, amount of adsorbed HCs). It is shown in this work how the data necessary to construct such models can be obtained in situ with the aid of the conceptual model and PM measurements over an inert open substrate

Hydrodeoxygenation (HDO) catalysts Characterization, reaction and deactivation studies

Production of biomass derived fuels such as renewable diesel, are primarily intended to reduce the reliance of the conventional engines on petroleum fuels as well as the emission of CO2 from fossil hydrocarbons. Hydrodeoxygenation (HDO) is a powerful technique that has been regularly used in the fuel upgrading processes. Sulfided molybdenum catalysts, supported on alumina and promoted by cobalt or nickel, are frequently used in the HDO processes. Despite the high efficiency of the HDO, catalyst activity and selectivity have raised major concerns from the economic and technological perspectives. The aim of this study was to gain a better understanding of the HDO catalyst structure, and then to assess the effect of different pretreatment and operational conditions on the catalyst activity and selectivity. The effect of preparation and pretreatment conditions on hydrogen uptake capacity and dispersion of the prepared Ni, Co and Mo containing catalysts was evaluated by using several characterization techniques such as BET, ICP-SFMS, SEM, TEM, TPO, ethylamine-TPD, XPS and H2-chemisorption. The H2-chemisorption, XPS and SEM results confirmed the detrimental effect of calcination on hydrogen uptake capacity of catalysts. The effect of pH of the impregnating solutions on the dispersion of the metal phases was also assessed from the TEM experiments. Moreover, HDO reactions of oleic acid and abietic acid over a prepared sulfided NiMo catalyst were studied. The results show that addition of DMDS to an oleic acid feed clearly promoted maintenance of the active sulfided phases on the NiMo catalysts. Higher concentration of DMDS also promoted the decarbonylation/decarboxylation (DCOx) route, and more importantly, decreased the amount of carbon deposition on the NiMo catalyst. On the other hand, addition of abietic acid to an oleic acid feed, is shown to decrease the deoxygenation rate of the oleic acid and increase the amount of carbon deposition on the catalyst. The inhibition effect of abietic acid on the HDO of oleic acid was related to stronger adsorption of the bulkier abietic acid molecules on the active sites compared to oleic acid that may have sterically hindered adsorption of oleic acid on neighboring sites. Furthermore, the poisoning effect of iron on the HDO of oleic acid over sulfided NiMo and Mo catalysts was investigated. It is shown that addition of iron to an oleic acid feed decreased the oxygenate conversion activity of both catalysts and changed their selectivities towards the final products. TEM results of the poisoned spent NiMo catalyst revealed that iron was mainly deposited on and in the vicinity of the Ni particles. This may also indicate that iron has reacted with Ni phase and as a result modified the catalyst activity. Finally, hydroconversion of rosin acids over supported NiMoS catalysts on alumina, USY-zeolite and mixed alumina/USY-zeolite was investigated. Various catalyst properties such as dispersion of the NiMo phases and Br\uf8nsted acidity affected the selectivity for the products. The results also indicate that the Br\uf8nsted acidity of the support could be optimized by the USY-zeolite content of the catalyst to achieve a satisfactory level of deoxygenation, ring opening and cracking of the rosin acid while avoiding excessive coke formation

Effects of Probiotic Cells on the Mechanical and Antibacterial Properties of Sodium-Caseinate Films

Background and Objective: Food processing conditions such as heat, mechanical or osmotic stress can lead to considerable losses of probiotics’ survival in food. Recently, the addition of probiotics into edible films has been proposed as an emerging technology for the delivery of probiotic cells. In this study, Lactobacillus acidophilus and Lactobacillus casei cells were incorporated into sodium caseinate matrix to develop a probiotic-based film which can improve food safety.Material and Methods: Probiotic cells were separately added to the film forming solutions and the active films were prepared by casting method. The physical, optical and mechanical characteristics of the films were examined. Color properties were determined using a colorimeter and the mechanical properties of the films were evaluated by an Instron Universal Testing Machine. The viability of Lactobacillus acidophilus and Lactobacillus casei in the films was determined during a period of 12 days. The antibacterial activities of the films were also tested against Listeria monocytogenes on Trypticase Soy Agar medium at 4°C.Results and Conclusion: Results demonstrated that lactic acid bacteria cells remained viable during a storage period of 12 days (> 4 Log CFU cm-2). The incorporation of lactic acid bacteria cells into the film polymer had no significant effect on tensile strength (p>0.05) whereas it significantly improves the appearance of films. Indeed, samples covered with the lactic acid bacteria film displayed higher anti-listerial activity than the control group on day 6 of preservation (p≤0.05). These findings show that the sodium caseinate film containing lactic acid bacteria cells can be used as a new effective packaging method for improving food safety

Towards stable nickel catalysts for selective hydrogenation of biomass-based BHMF into THFDM

Selective transformation of BHMF (2,5-bis(hydroxymethyl)furan) to THFDM (tetrahydrofuran-2,5-dimethanol) over a variety of structured Ni/Sx-Z1−x catalysts was investigated. The effects of support, Ni loading, solvent, temperature, pressure, and particle size on the conversion and selectivity were studied. Among them, the 10 wt% Ni catalyst supported on the SiO2:ZrO2 weight ratio of 90:10 (10NiS90Z10) exhibits the best performance in terms of BHMF conversion and THFDM selectivity. Its good performance was attributed to its well-balanced properties, that depend upon the ZrO2 content of the support in combination with SiO2, the active Ni sites-support interaction, and acidity/basicity ratio of each catalyst resulting in different Ni dispersions. Importantly, the 10NiS90Z10 catalyst showed a stable selectivity to THFDM (>94%), with 99.4% conversion of BHMF during 2 h reaction time. Poor catalytic activity resulted from excessive ZrO2 content (>10 wt%). The structural, textural, and acidity properties of NiSi100−y-Zry catalysts, tuned by selectively varying the Ni amount from 5 to 15 wt%, were critically investigated using numerous material characterization techniques. Catalyst recycling experiments revealed that the catalyst could be recycled several times without any measurable loss of catalytic activity

Effect of DMSO on the catalytical production of 2,5-bis(hydoxymethyl)furan from 5-hydroxymethylfurfural over Ni/SiO2 catalysts

Hydroconversion of 5-hydroxymethylfurfural (HMF) to 2,5-bis(hydoxymethyl)furan (BHMF) was studied over mono- and bimetallic supported catalysts. It was found that monometallic Ni/SiO2 catalysts exhibited superior performance with a total yield of BHMF of up to 99 wt%. This excellent performance may be attributed to higher Ni dispersion and low acidity of the support. Dimethyl sulfoxide (DMSO) is often present in HMF, due to the route used for its synthesis. DMSO adsorption caused a clear reduction of Ni/SiO2 performance for the HMF hydrodeoxygenation reaction. Characterization of the spent catalysts was performed using HAADF-STEM-EDX, Raman, ICP, and XPS spectroscopies, and showed the presence of sulfur and graphitic carbon, which could explain the deactivation

The effects of chitosan coating combined with natamycin on quality of salted kutum (Rutilus frisii kutum) roe during refrigerated storage

The effects of chitosan (Ch) (Medium molecular weight chitosan) coating combined with natamycin (Ch+ N) on quality of salted kutum (Rutilus frisii kutum) roe (treated with 4% NaCl salt) during refrigerated storage (4±1°C) were studied over a period of 90 days. A solution of Ch (1%, w/v) and Ch+ N (1%, w/v Ch +5 and 10 mg natamycin per Kg salted roe) was used for the coating. The control (salted roe) and the coated roe samples were analyzed periodically (0. 30, 60 and 90 days) for chemical (TVB-N, PV and TBA), remaining salt and pH characteristics. The results indicated that the chitosan coating enhanced the storage quality of the kutum salted roe as compared to an uncoated salted roe (control). Chitosan coating combined with natamycin afforded better protection than chitosan coating for chemical parameters (TVB-N, PV and TBA). Remaining salt was determined lower than 2% for all treatment. The conclusion was showed the combination of chitosan coating and natamycin at a 10 mg per Kg of roe were increased shelf life of the kutum roe

Influence of liposome encapsulated essential oils on properties of chitosan films

[EN] The effect of the encapsulation of eugenol and cinnamon leaf essential oil (CLEO) in lecithin liposomes on the losses of these compounds during the chitosan film formation process by casting was evaluated. Film-forming dispersions and films with eugenol or CLEO (either free or encapsulated) were obtained and characterized. The content of eugenol in active films was quantified by means of solvent extraction and gas chromatograph analysis. The encapsulation of eugenol or CLEO in lecithin liposomes led to the films retaining 40% −50% of the incorporated eugenol, whereas only 1%−2% was retained when eugenol was incorporated by direct emulsification. Films with liposomes exhibited a lamellar microstructure which improved film extensibility and increased water vapour barrier capacity with respect to those with free emulsified compounds. Liposomes also modified the optical properties of the films, reducing their gloss, increasing colour saturation and making them redder in colour. The encapsulation of volatile active compounds in liposomes appears to be a good strategy for obtaining antimicrobial films with essential oils.The authors acknowledge the financial support provided by the Ministerio de Economía y Competitividad (Project AGL2013-42989-R). Cristina Valencia Sullca thanks the Programa Nacional de Becas del Perú (Pronabec) for the completion of her doctoral thesis.Valencia-Sullca, CE.; Jiménez Serrallé, M.; Jiménez Marco, A.; Atarés Huerta, LM.; Vargas, M.; Chiralt, A. (2016). Influence of liposome encapsulated essential oils on properties of chitosan films. Polymer International (Online). 65(8):979-987. https://doi.org/10.1002/pi.5143S979987658Jiménez, A., Fabra, M. J., Talens, P., & Chiralt, A. (2013). Physical properties and antioxidant capacity of starch–sodium caseinate films containing lipids. Journal of Food Engineering, 116(3), 695-702. doi:10.1016/j.jfoodeng.2013.01.010Zhai, M., Zhao, L., Yoshii, F., & Kume, T. (2004). 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